Presently, known cooling devices and processes for cooling an internal-combustion engine of a motor vehicle employ oil cooled by means of a coolant. There are various kinds of cooling devices which are differentiated in regard to the coolant. One cooling device in accordance with the prior art is the air-oil cooler. This is arranged at the front of the motor vehicle in the air flow produced by the movement of the vehicle.
The disadvantage of this solution is that the coolant being used—the air—has a relatively low heat transmission coefficient. In order to implement an adequate oil-cooling system, an air-oil cooler of relatively large construction is therefore necessary. In addition, the cooling process is dependent on the air flow and thus on the speed at which the motor vehicle is travelling. At low speeds of travel, the air-oil cooler does not provide sufficient cooling power. The oil must be fed to the air-oil cooler. To this end, flexible lines from the engine to the air-oil cooler have to be employed due to the distances that have to be bridged and the flexible path required for the conveyance of the oil. These flexible lines, which are usually in the form of hoses, are inclined to leak after a long period of use.
Another cooling device in accordance with the prior art is the oil-water heat exchanger. This uses water or cooling water as the cooling medium. Due to the higher heat transmission coefficient of water, this heat exchanger has greater cooling power while occupying lesser space. The coolant, more precisely, the water, and the oil are fed through a line system consisting of hoses or pipes. The use of pipes and hoses is disadvantageous in regard to the interconnections of the pipes and hoses or the connections thereof to the engine or the oil-water heat exchanger since the connections tend to leak relatively quickly, particularly at the junction points. Furthermore, the mechanical flow properties of the connections are disadvantageous since the connections lead in part to large resistances in the line system.
A third cooling device in accordance with the prior art is the oil-water heat exchanger module with an oil filter. This solution overcomes some of the disadvantages of the previously-specified cooling devices. The advantage of the modular construction is that the oil-water heat exchanger module is of compact construction. The oil filter is in the form of a filter cartridge which is flanged on the heat exchanger. The oil line system is in the form of a channel integrated into the module housing, whereby the risk of leakage from the oil line is significantly reduced.
The disadvantage of this solution is that, here too, the coolant in the form of water is fed and guided through hoses. Consequently, leakage from the water pipeline may continue to occur. In addition, vibratory problems may occur during the operation of the motor vehicle due to the heavy concentration of components within a small constructional space, and these can lead to the failure of the cooling device in some circumstances.
In all of the solutions specified above, the current-flow of the media—coolants/oil—flowing in the channels is effected in succession, i.e. in a kind of series circuit. The channels are thereby of greater length; this thus leads to a larger constructional volume. In addition, the line system is of greater total resistance due to the length of the channels, so that this too has to be compensated for by a larger dimensioning of the flow-path cross-sections of the line system if there is to be no loss of performance. However, apart from the cooling function thereof, a goal of such cooling systems is to maintain the pressure difference in the cooling module as low as possible since this itself adds to the overall drop in pressure through the entire engine system and a decrease in pressure represents a loss of effectiveness. The greater the decrease in pressure, the higher the loss of effectiveness. In order to ensure this in the conventional systems, the cooling medium flows through the cooling module at high speed, i.e. it spends a lesser period of time in the cooler module or cooler package, whereby the cooling medium can absorb and remove only a little of the heat energy and this thus results in a less effective cooling process. In addition, due to the serial arrangement, the water circulation systems in the cylinder block and in the cylinder head must be adjusted separately, i.e. it is necessary for the circulation of the water in the cylinder block and the cylinder head to be readjusted. Additional expenditure on the adjustment process thereby arises.